package cn.fay.chapter18;

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.nio.IntBuffer;
import java.nio.channels.FileChannel;

public class MappedIO {
	private static int numOfInts=4000000;
	private static int numOfUbuffInts=200000;
	
	private abstract static class Tester{
		private String name;
		public Tester(String name) {
			this.name=name;
		}
		public void runTest() {
			System.out.print(name+": ");
			try {
				long start = System.nanoTime();
				test();
				double duration=System.nanoTime()-start;
				System.out.format("%.2f\n", duration/1.0e9);
			} catch (IOException e) {
				throw new RuntimeException(e);
			}
		}
		public abstract void test() throws IOException;
	}
	private static Tester[] testers=new Tester[6];
	static{
		
		testers[0]=new Tester("Stream Write") {
			public void test() throws IOException {
				DataOutputStream dos=new DataOutputStream(new BufferedOutputStream(
						new FileOutputStream(new File("temp.tmp"))));
				for(int i=0;i<numOfInts;i++){
					dos.writeInt(i);
				}
				dos.close();
			}
		};
		
		testers[1]=new Tester("Mapped Write") {
			public void test() throws IOException {
				FileChannel fc = new RandomAccessFile("temp.tmp", "rw").getChannel();
				IntBuffer intBuffer = fc.map(FileChannel.MapMode.READ_WRITE, 0, fc.size()).asIntBuffer();
				for (int i = 0; i < numOfInts; i++) {
					intBuffer.put(i);
				}
				fc.close();
			}
		};
		
		testers[2]=new Tester("Stream Read") {
			public void test() throws IOException {
				DataInputStream dis=new DataInputStream(new BufferedInputStream(
						new FileInputStream("temp.tmp")));
				for (int i = 0; i < numOfInts; i++) {
					dis.readInt();
				}
				dis.close();
			}
		};
		
		testers[3]=new Tester("Mapped Read") {
			public void test() throws IOException {
				FileChannel fc = new FileInputStream("temp.tmp").getChannel();
				IntBuffer intBuffer = fc.map(FileChannel.MapMode.READ_ONLY, 0, fc.size()).asIntBuffer();
				while (intBuffer.hasRemaining()) {
					intBuffer.get();
				}
				fc.close();
			}
		};
		
		testers[4]=new Tester("Stream Read/Write") {
			public void test() throws IOException {
				RandomAccessFile raf=new RandomAccessFile("temp.tmp", "rw");
				raf.writeInt(1);
				for (int i = 0; i < numOfUbuffInts; i++) {
					raf.seek(raf.length()-4);
					raf.writeInt(raf.readInt());
				}
				raf.close();
			}
		};
		
		testers[5]=new Tester("Mapped Read/Write") {
			public void test() throws IOException {
				FileChannel fc = new RandomAccessFile("temp.tmp", "rw").getChannel();
				IntBuffer intBuffer = fc.map(FileChannel.MapMode.READ_WRITE, 0, fc.size()).asIntBuffer();
				intBuffer.put(0);
				for (int i = 1; i < numOfUbuffInts; i++) {
					intBuffer.put(intBuffer.get(i-1));
				}
				fc.close();
			}
		};
	}
	
	public static void main(String[] args) {
		for (Tester tester : testers) {
			tester.runTest();
		}
	}
}
